1. Technical Field
The present invention relates to a recorder/reproducer intended for preventing an unauthorized use of content data and to a content data protection system that includes a portable medium, and particularly to technology for improving user convenience while preventing an unauthorized use of content data.
2. Background Art
With the commencement of BS digital broadcasting and terrestrial digital broadcasting, recent years have seen digital contents such as movies being extensively distributed. Since digital contents (hereinafter referred to as content data) are easy to replicate, there is rising concern for illicit acts such as unauthorized replication of content data protected by copyright and distribution of replicated content data over the Internet or on a recording medium or the like. Under these circumstances, there has been a technological development underway to suppress such illicit acts. Digital Transmission Content Protection (DTCP) is an example of such technology for protecting content data protected by copyright.
DTCP is a technology for preventing unauthorized copying of content data protected by copyright, such as by encrypting the content data when the content data is digitally transferred. In a content data protection technology such as DTCP, copy control information is given to content data.
Meanwhile, there is a demand for moving content data to another recording medium or another device even if the copying of such content data is prohibited by copy control information. For example, there is a case where content data protected by copyright recorded in a hard disc drive (HDD) included in a digital television, a recorder, or the like is wished to be moved to a portable recording medium such as a DVD-RAM, a Secure Digital (SD) card, in order to store such content data as a master copy. In this case, when the content data protected by copyright is moved from the HDD to a DVD-RAM, it is of course necessary to delete or to make irreproducible such content data protected by copyright recorded in the HDD.
Thus, it is a disadvantage to a user of the content data if both of the copy-source content data and the destination content data are lost in the middle of moving the content data, due to such factors as power breakdown, and they consequently become unusable as content data. Furthermore, it also generates an economic damage if the user needs to spend money to obtain again the same content data as the one that has become unusable.
In response to this, there is proposed a technology that allows content data to be moved without causing the loss of such content data, while preventing unauthorized copying of the content data (for example, refer to Patent Document 1).
Patent Document 1: Japanese Laid-Open Patent Application No. 2003-228522
However, in the case where the copy-source content data is content data with high image quality, and the recording capacity of the copy-destination is small compared with the size of the content data, such content data is usually moved after being compressed to a smaller size by degrading its image quality or the like before being moved. Thus, when the copy-source content data is invalidated, only the content data whose image quality has been degraded through compression conversion is left for the user. In other words, even when the content data is returned again to an HDD with a larger recording capacity, a high image quality of such content data cannot be restored, which results in the loss of the advantage of the user using such content data.
Furthermore, in the case where the content data is moved from an HDD to a portable recording medium, time required for moving the content data becomes longer, if such content data is moved simultaneously with the compression conversion, which results in the loss of the advantage of the user.
The present invention has been conceived in view of the above problems, and it is an object of the present invention to provide a recorder/reproducer and a content data protection system capable of: allowing for the moving of content data without causing the loss of the content data, while preventing unauthorized copying; restoring the original high image quality of the content data, even when its size is reduced through compression conversion, in the case of returning the content data to the copy-source; and allowing for an easy moving of the content data to a portable recording medium or to another recorder/reproducer.